1. Field of the Invention
The present invention relates to photographic apparatus, and more particularly, to a double exposure prevention mechanism that cooperates with a shutter driving member and a film advance member.
2. Description of the Prior Art
In cameras of the type having self-cocking shutters, i.e., shutters which are automatically cocked upon return of the body release member, it is known to employ means for disabling the shutter after an exposure and prior to the advance of the exposed film in order to prevent double exposure. Generally, such double exposure prevention means have taken the form of linkage adapted to block the body release member of the camera after an exposure and to free the body release member upon subsequent advancement of exposed film. (See U.S. Pats. No. 636,036 and 2,722,872)
Some of the double exposure prevention mechanisms of the above-described type have the drawback that if the camera operator attempts to overcome the blocking force on the body release member, damage to the camera mechanism may result. It may further be undesirable to block the movement of the body release member if the body release member is adapted to perform auxiliary functions upon partial movement towards its exposure initiating position, e.g., partial depression of the body release member may actuate such auxiliary functions as battery check or low light level signal. The photographer may wish to operate these functions after an exposure but prior to the next film advance.
Recently, photographic apparatus has been developed having a double exposure prevention latch that cooperates with a piezoelectric flash firing spring to disable the driving member of a self-cocking shutter when the piezoelectric operator is not cocked. (See U.S. Pat. appliction Ser. No. 678,271, entitled DOUBLE EXPOSURE PREVENTION DEVICE, filed Apr. 19, 1976 in the names of William T. Hochreiter and Fredric A. Mindler now U.S. Pat. No. 4,052,730 issued Oct. 4, 1977). In this device, the body release member may be fully depressed after the exposure but prior to subsequent film advance without actuating the shutter. In cameras wherein the piezoelectric generator is not cocked until the film is advanced, this approach works very well, however, in cameras where the piezoelectric generator is self-cocking upon return of the body release member, the above-noted approach is not applicable. Such a camera is described in the above-referenced copending U.S. Pat. applications.
The present invention is directed to a double exposure prevention device for use in such a camera.